1. Field of the Invention
This invention relates to a signal processing system having a signal processing device and an external storage device which is arranged to be attachable to and detachable from the signal processing device.
2. Description of the Related Art
In recording a video signal obtained by sensing images with a video camera and an audio signal obtained simultaneously with the video signal, many systems have been arranged to enhance the image effect of the record by superimposing or combining some other images such as letters, symbols, a specific picture or the like with the recording video signal and to multiplex background music or some effect sounds with the recording audio signal.
Among various known systems for combining video signals with other signals, a system of using a so-called character generator has been often employed. This system comprises: a pattern ROM (read-only memory) which stores various patterns such as characters, symbols, etc. for a display as necessary; registers which are arranged to store information on the kind of a character to be displayed in every one of display positions; and a reading part which is arranged to read out the contents of the pattern ROM corresponding to the contents of the registers in accordance with horizontal and vertical synchronizing (sync) signals and to combine them with the video signal. Further, in displaying a character, the kind of the character to be displayed is written into the register of the display position by means of a microcomputer or the like.
In the case of another known system, the video signal obtained by sensing images is converted by an A/D (analog-to-digital) converter into a digital image signal of one to several bits. The digital image signal is stored in a memory arranged for every display picture element. Then, in accordance with the horizontal and vertical sync signals, the contents of the memory are serially read out to combine them with another video signal which is separately obtained by sensing images.
A further example of known systems comprises: a graphic memory which corresponds to each picture element on a picture plane; a microcomputer which writes image data to be displayed into the graphic memory; and a reading circuit which reads out the contents of the graphic memory. The microcomputer is arranged to write the image data to be displayed into the graphic memory in accordance with a given program. The reading circuit is arranged to read out the image data in accordance with horizontal and vertical sync signals. The data thus read out is combined with a video signal obtained by shooting.
As regards the method for inserting some other audio signal into an audio signal obtained at the time of image sensing, a device for generating an audio signal such as a music record, a music tape, an electronic sound generator, or the like is used in many cases. After image sensing with a video camera, the audio signal obtained by the audio signal generating device is combined by means of a mixing amplifier or the like with sounds recorded as an audio signal on a tape along with a video signal while the audio signal recorded on the tape is reproduced.
Meanwhile, methods of varied kinds have been proposed for controlling a video camera including, for example, a method wherein a memory or a microcomputer which is arranged to store, for example, aperture values, white balance adjustment values, focal points, electronic shutter time values, etc., is disposed within the video camera. A suitable combination of these values is then selected by means of a selection switch or the like for controlling the shooting operation of the camera.
However, discrete devices of varied kinds must be used for inserting a specific image into a video signal obtained by shooting, for inserting a given audio signal into the sounds obtained by shooting and for controlling the shooting operation of the video camera as mentioned above. In addition to that, connection lines are necessary for interconnecting these discrete devices. Therefore, it has been extremely difficult for general amateurs to carry out these inserting operations.